1. Field of this Invention
This invention relates to a process for producing ductile, superconductive alloys by incorporating one or more superconductive compounds by fusion in a base metal having good electrical and heat conductive properties; for example, copper, silver, aluminum, or the like. In the process of this invention, the individual particles of the superconductive compound or compounds are finely distributed in the base metal and are mutually spaced apart in such a way that the critical value for the tunnel effect is not exceeded.
2. Prior Art
A process for producing ductile, inherently stable, superconductive wires is already known wherein the starting materials consist of alloys on a copper or aluminum base with superconductive intermetallic compounds, such a niobium and tin, incorporated therein by fusion (see German Patent 2,116,260). In this known process, elongated deposits, for example, of the intermetallic compound Nb.sub.3 Sn are obtained by directional solidification. The alloy which is produced in this way can be processed by wire drawing porcesses, inter alia, to form superconductive wires. In the course thereof, it is essential that the spaces between the extended precipitates are minimized to such an extent by the deformation process that they can be superconductively bridged by the tunnel effect.
C. C. Tsuei, Science, vol. 180 Apr. 6, 1973), pp. 57-58, describes a very similar process. Similarly, according to Tsuei, superconductive properties can only be obtained with cast alloys of composition corresponding to those cited in the above-mentioned German patent (alloys on the quasi binary section Cu-Nb.sub.3 Sn) if the solidified alloys are extended by means of rollers and/or the wire drawing process and the incorporated particles of superconductive compounds are drawn sufficiently closely together for the particle spacing dictated by the tunnel effect to be attained or not exceeded. In addition, the annealing treatment indicated in Tsuei, which is carried out for 5 hours at 800.degree. C., does not raise the superconductivity of these alloys in the unworked state to in excess of 5.degree. K.
However, on account of the directional solidification in particular, the known processes are subject to the disadvantage of only being suitable for producing cast elements of relatively small dimensions which are, in fact, too small for many applications. In addition, these known processes are practically limited to the production of thin wires or wire-like structures as the superconductive alloys can only be produced by rolling and wiredrawing processes in which the incorporated particles of superconductive compounds are arranged parallel to each other and drawn sufficiently closely together (parallel flow lines) for the mutual spacing to be bridged by the tunnel effect.
The workability of thin wires and of other products produced by the known processes is therefore very limited as it is necessary to insure, during the subsequent working processes, that the tunnel effect which is decisive for superconductivity is maintained and that the flow lines will continue to run parallel to each other, that is, even after further working.